Scanning electron microscopy (SEM) provides high-resolution images of fracture surfaces or important insights into the concentration and distribution of chemical elements in the material being studied.

Materials Engineering has been using a focused ion beam (FIB) for four years now. This makes the brand with the four rings a pioneer among car manufacturers. The combination of an imaging scanning electron microscope and an ion gun as an abrasive tool makes it possible to create high-resolution, cross-sectional images of material systems.

The functional principle of the focused ion beam: the gallium ion beam of the FIB first digs a hole invisible to the human eye into the material under investigation. An integrated scanning electron microscope then provides a high-resolution, cross-sectional view below the material surface. The typical cutting depths of 5 to 50 micrometers – with widths of 50 to 100 micrometers – are achieved after two to five hours of cutting time. A major advantage is that the experts can follow the cutting process live with the scanning electron microscope.

At the same time, compared with mechanical preparation methods like the creation of grinding patterns, the FIB offers the big advantage in the case of complex material combinations (e.g. hard, thin coating of soft substrates) of only leaving behind minimal preparation artifacts. This refers to changes of a distorting nature, such as those on interfaces which result from such preparation.

In addition to the typical analyses in the field of surface technology, such as anti-corrosion coatings and paints, Audi uses FIB technology for almost all automotive-relevant raw materials and material systems: metal, glass, ceramics, polymers and even leather.

Exemplary overview of areas of application for FIB analysis at Audi Materials Engineering; new fields of application with high potential for the future are highlighted in red

FIB analysis technology has particular potential for the new material challenges in electrification and digitalization. For example, a targeted and high-resolution SEM analysis of the individual layers of a touch-sensitive screen is only possible with an ion-based sample preparation. Possible weaknesses on interfaces of the individual layers which can lead to functional defects, can therefore be identified at an early stage in the development process.

The pressure tanks made of CFRP and GFRP fulfill the strict safety requirements prescribed by law. Before the start of series production, the materials engineering experts at Quality Assurance carried out elaborate analyses as part of shakedown testing. This ensures that the energy stores of the new g-tron models will function flawlessly even after many years and tens of thousands of kilometers in the hands of customers.

Material analysis in detail

For the material experts, computed tomography is the non-destructive testing method of choice in a first analysis step. This technology allows, for example, fiber damage within the composite material to be made visible and measurable.

Microsections are prepared for further investigations of the pressure tanks. A section of the tank is cut out, one of its edges finely polished and then examined under the microscope. With this method, the tank’s composite material can be examined optically for pore size and distribution.

An additional thermal process (calcination) allows an exact determination of the porosity and a check of the proportion of glass fibers and carbon fibers. DSC analysis (differential scanning calorimetry) determines the softening temperature of the resin. This enables the experts to investigate the durability of the material after many thousands of kilometers.

In addition, the CNG tanks undergo further optical inspections and material analyses in the laboratory. One of these is tensile testing to determine the mechanical properties of the inliner, a special gas-tight blow-molded plastic part.

Sustainable: leather tanned using plant substancesAudi is a pioneer in the use of chrome-free tanned leather in the entire vehicle interior – and that since more than 20 years. Now follows the next step towards even more environmentally friendly use of resources: the brand with the four rings uses leather tanned using plant substances. This patented process uses olive leaf extract. The materials experts check and follow the diverse process steps from soaking to drying and staining, right up to the finished product – olive-leaf tanned leather.

* Figures depend on the tire/wheel set used and the transmission variant

The specified fuel consumption and emission data have been determined according to the measurement procedures prescribed by law. Since 1st September 2017, certain new vehicles are already being type-approved according to the Worldwide Harmonized Light Vehicles Test Procedure (WLTP), a more realistic test procedure for measuring fuel consumption and CO2 emissions. Starting on September 1st 2018, the New European Driving Cycle (NEDC) will be replaced by the WLTP in stages. Owing to the more realistic test conditions, the fuel consumption and CO2 emissions measured according to the WLTP will, in many cases, be higher than those measured according to the NEDC. For further information on the differences between the WLTP and NEDC, please visit
www.audi.de/wltp.

We are currently still required by law to state the NEDC figures. In the case of new vehicles which have been type-approved according to the WLTP, the NEDC figures are derived from the WLTP data. It is possible to specify the WLTP figures voluntarily in addition until such time as this is required by law. In cases where the NEDC figures are specified as value ranges, these do not refer to a particular individual vehicle and do not constitute part of the sales offering. They are intended exclusively as a means of comparison between different vehicle types. Additional equipment and accessories (e.g. add-on parts, different tyre formats, etc.) may change the relevant vehicle parameters, such as weight, rolling resistance and aerodynamics, and, in conjunction with weather and traffic conditions and individual driving style, may affect fuel consumption, electrical power consumption, CO2 emissions and the performance figures for the vehicle.

Further information on official fuel consumption figures and the official specific CO2 emissions of new passenger cars can be found in the “Guide on the fuel economy, CO2 emissions and power consumption of new passenger car models”, which is available free of charge at all sales dealerships and from DAT Deutsche Automobil Treuhand GmbH, Hellmuth-Hirth-Str. 1, D-73760 Ostfildern, Germany and at
www.dat.de.